System and method for reducing core of a metallic honeycomb panel structure

ABSTRACT

A method and system for forming a honeycomb panel structure. The method includes the steps of compressing the honeycomb panel structure in a first panel region and reinforcing the first panel region. Reinforcing the first panel region may include the steps of drilling a plurality of holes in the first panel region; inserting pins into the first panel region; and welding pins into a face sheet of the honeycomb panel structure. Alternatively, the step of reinforcing the first panel region may include the step of adding an additional face sheet to the honeycomb panel structure.

FIELD

The present disclosure relates to metallic sandwich structures such ashoneycomb panel structure. More specifically, the present disclosurerelates to methods and apparatus for reducing or compressing a core of ahoneycomb panel structure.

BACKGROUND

Metallic honeycomb panels or sandwich structures have been increasinglyused on advanced designs for vehicles such as aircraft and ships.Reasons for using metallic sandwich structures include saving weight ascompared to steel structures, reducing radar cross section increasingcorrosion resistance, and reducing life cycle costs.

Although such sandwich structures can offer certain superior bendingstiffness properties over other design configurations, one issue thatmay tend to limit the usage of sandwich structures is the difficulty ofattaching the structure to adjacent structures or attachment fittingswith adequate load transfer at the attachment region without undueincrease in weight and cost. While in certain situations it can berelatively easy to attach sandwich structures when the applied loads arelow, it is quite a challenge to do so for highly loaded structure.

Various honeycomb attachment procedures have been developed. Forexample, one method of joining structural members such as metallicstructural members utilizes a core ramp down region. In such a process,the honeycomb core residing between the facing sheets must be eliminatedeither through the fabrication of the core or must be machined downafter core manufacturing. Such processes are expensive, they also stillrequire some type of attachment fitting between the honeycomb panel andsome other supporting structure, and may be prone to certain heightenedfailure modes if the ramp down is either too steep or too shallow.

Alternatives to core ramp-down include the use of mechanical inserts,bushings, or other types of mechanical attachment fittings that must beintegrated within the panel. However, the use of such attachmentfittings can also present certain shortcomings. For example, to installcertain fittings within a panel, a section of the panel must be cut outand a machined fitting is inserted into the panel or must be welded tothe face sheets of the panel. This increases the overall cost of thesandwich structure while also increasing the time to manufacture aswell.

There is, therefore, a need for a more cost effective and less laborintensive method of assembling honeycomb core structures. Such a desiredcost effective and less labor intensive assembled structures should alsooffer a more robust and efficient method of providing a seal to theedges of a honeycomb panel while also increasing manufacturing facilitythroughput while also driving down overall system manufacturing costs.

SUMMARY

According to an exemplary arrangement, a method and system for forming ahoneycomb panel structure is presented. The method includes the steps ofcompressing the honeycomb panel structure in a first panel region andreinforcing at least a portion the first panel region. Reinforcing thefirst panel region may include the steps of drilling a plurality ofholes in the first panel region; inserting pins into the first panelregion and welding the pins into a face sheet of the honeycomb panelstructure. Alternatively, the step of reinforcing the first panel regionmay include welding an additional face sheet to the pins of thehoneycomb panel structure.

The step of reinforcing at least a portion of the first panel region mayalso comprise the steps of utilizing at least one welded pin to add atleast one additional face sheet to the honeycomb panel structure. In onearrangement, the honeycomb panel comprises a metallic honeycomb panel.The method may also include the step of drilling a plurality of holes inan uncompressed panel region adjacent the first panel region; insertinga second plurality of pins into the un-compressed panel region; andwelding the second plurality of pins into a face sheet of the honeycombpanel structure. In addition, the method may comprise the step ofinserting the second plurality of pins into the panel regionsubstantially vertical to a bottom face sheet of the honeycomb panelstructure.

In one arrangement, the method may include the step of attaching atleast one additional face sheet to at least a portion of the compressedcore region. The method may also include the step of completelycompressing the honeycomb panel structure in the first region.Alternatively, the step of compressing the honeycomb panel structure maycomprise the step of partially compressing the honeycomb panel structurein the first region.

The features, functions, and advantages can be achieved independently invarious embodiments of the present disclosure or may be combined in yetother embodiments in which further details can be seen with reference tothe following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrativeembodiments are set forth in the appended claims. The illustrativeembodiments, however, as well as a preferred mode of use, furtherobjectives and descriptions thereof, will best be understood byreference to the following detailed description of an illustrativeembodiment of the present disclosure when read in conjunction with theaccompanying drawings, wherein:

FIG. 1 illustrates an exploded perspective view of one of theembodiments of a honeycomb panel structure of the disclosure;

FIG. 2 illustrates a fully assembled perspective view of the honeycombpanel structure illustrated in FIG. 1;

FIG. 3 illustrates a perspective view of one of the embodiments of ahoneycomb panel structure with a compressed core region;

FIG. 4 illustrates a close up view of the honeycomb panel structure witha compressed core region illustrated in FIG. 3;

FIG. 5 illustrates a perspective view of another embodiment of ahoneycomb panel structure with a compressed core region;

FIG. 6 illustrates a close up view of the honeycomb panel structure witha compressed core region illustrated in FIG. 5;

FIG. 7 illustrates a perspective view of another embodiment of ahoneycomb panel structure with a compressed core region;

FIG. 8 illustrates an alternative view of the honeycomb panel structurewith a compressed core region illustrated in FIG. 7;

FIG. 9 illustrates a perspective view of another embodiment of ahoneycomb panel structure with a compressed core region;

FIG. 10 illustrates an alternative view of the honeycomb panel structurewith a compressed core region illustrated in FIG. 9;

FIG. 11 illustrates a perspective view of another embodiment of ahoneycomb panel structure with a compressed core region;

FIG. 12 illustrates an alternative view of the honeycomb panel structurewith a compressed core region illustrated in FIG. 11;

FIG. 13 illustrates a perspective view of another embodiment of ahoneycomb panel structure with a compressed core region;

FIG. 14 illustrates an alternative view of the honeycomb panel structurewith a compressed core region illustrated in FIG. 13;

FIG. 15 illustrates a perspective view of another embodiment of ahoneycomb panel structure with a compressed core region;

FIG. 16 illustrates an alternative view of another embodiment of ahoneycomb panel structure with a compressed core region;

FIG. 17 illustrates a perspective view of another embodiment of ahoneycomb panel structure with a compressed core region;

FIG. 18 illustrates an alternative view of the honeycomb panel structurewith a compressed core region illustrated in FIG. 17;

FIG. 19 illustrates a perspective view of another embodiment of ahoneycomb panel structure with a compressed core region;

FIG. 20 illustrates an alternative view of the honeycomb panel structurewith a compressed core region illustrated in FIG. 19;

FIG. 21 is an illustration of a flow diagram of an embodiment of amethod of the disclosure for making one of the embodiments of thecompressed honeycomb panel structure of the disclosure;

FIG. 22 illustrates one compression arrangement for compressing ahoneycomb panel structure; and

FIG. 23 illustrates the compression arrangement of FIG. 21 compressing ahoneycomb panel structure in accordance with one aspect of thedisclosure.

DETAILED DESCRIPTION

Disclosed embodiments will now be described more fully hereinafter withreference to the accompanying drawings, in which some, but not all ofthe disclosed embodiments are shown. Indeed, several differentembodiments may be provided and should not be construed as limited tothe embodiments set forth herein. Rather, these embodiments are providedso that this disclosure will be thorough and complete and will fullyconvey the scope of the disclosure to those skilled in the art.

The present disclosure provides for embodiments of a metallic honeycombpanel structure having at least one reduced or compressed honeycomb coreregion and a method for making the same. Embodiments of the structureand method may be used in aircraft, spacecraft, motor craft, watercraft,and other craft, as well vehicles and other similar structures. Inaddition, embodiments of the structure and method may be used withintegrated commercial building materials for both cooling applications,as well as energy harvesting from lightweight structures.

FIG. 1 is an illustration of an exploded perspective view of one of theembodiments of an un-crushed or an un-compressed metallic honeycombpanel structure 50 of the disclosure. FIG. 2 is an illustration of afully assembled perspective view of the integrated metallic structure 50of FIG. 1. In one of the embodiments of the disclosure, there isprovided the metallic structure 20. The metallic structure 20 comprisesa first or top face sheet 22 having an interior side 24 and an exteriorside 26. The embodiment of the metallic construction 20 illustrated inFIG. 2 comprises at least one substantially planar or flat portion.However, as will be discussed below, in other embodiments, theconstruction 20 may have one or more curvatures and may be formed into avariety of non-planar shapes. In addition, although the metallicconstruction 20 is illustrated as having a constant height, alternativemetallic constructions having non-uniform height may also be used.

The metallic structure 20 further comprises a second or bottom facesheet 28 having an interior side 30 and an exterior side 32. Preferably,the first or top face sheet 22 and the second or bottom face sheet 28may also be comprised of metal materials, such as aluminum, titanium orany another suitable metal or another suitable material. The thicknessof the first and second face sheets 22, 28 may preferably be from about0.005 inch to about 0.1 inch thick or of another suitable thickness.Alternatively, the first face sheet 22 and the second face sheet 28comprise metallic materials. Suitable metallic materials may comprisealloys of titanium, aluminum, steel or corrosion resistant steel oranother suitable alloys. The first and second face sheets 22, 28 maycomprise the same metallic material or dissimilar material. In addition,the first and second face sheets 22, 28 may comprise the same or adifferent thickness.

The metallic structure 20 further comprises a honeycomb core 34assembled between the first face sheet 22 and the second face sheet 28.Typically, the honeycomb core may be either resistance welded or brazedto the first and second face sheets 22 and 28, respectively. Thehoneycomb core 34 has a first end 36 adjacent the interior side 24 ofthe first face sheet 22. The honeycomb core 34 has a second end 38adjacent the interior side 30 of the second face sheet 28. A localizedregion/area or center portion 44 of the core resides between a first end50 and a second end 60 of the honeycomb panel 20. The honeycomb core 34has first sides 40 and second sides 42. The honeycomb core 34 maycomprise cells 43 having a hexagonal shape. Hexagonal cells provide aminimum density for a given amount of material comprising the honeycombcore. Alternatively, the honeycomb core may comprise cells havinganother suitable shape.

As will be described in greater detail below, the present disclosurerelates to methods and systems for taking a honeycomb panel structure(such as the structure illustrated in FIGS. 1 and 2) undergoing acontrolled compress or crush of a core region of the honeycombstructure. The compressed core region may be located at one or both endsof the honeycomb panel (e.g., at ends 50, 60) and/or may be provided atthe localized region/area or center 44 of the core. In addition, ifcalled for by the structure specification and design, the disclosedmethod and system may provide one or more structural reinforcements tothe compressed honeycomb panel. Such a structural reinforcement maycomprise pins and/or doublers (i.e., one or more additional face sheets)to the honeycomb panel. If one or more pins are used, such pins may beof similar or dissimilar materials and/or mechanical properties.Similarly, if one or more additional face sheets are used, suchadditional face sheets may comprise similar or dissimilar materials ormechanical properties.

FIG. 3 illustrates a first arrangement of a honeycomb panel structure100 comprising a compressed core region 102. FIG. 4 illustrates a closeup view of the compressed core region 102 of the honeycomb panelstructure 100 illustrated in FIG. 3. The honeycomb panel structure 100illustrated in FIGS. 3 and 4 comprises essentially the same structure ofthe honeycomb panel structure illustrated in FIGS. 1 and 2. That is,this honeycomb panel structure 100 comprises a honeycomb core assembledbetween a first or top face sheet 110 and a second or bottom face sheet114 and a honeycomb core 120 residing between these two sheets. For easeof illustration, in FIGS. 3 and 4, a portion of the honeycomb core 120between the top face sheet 110 and the bottom sheet 114 along the firstand second inclines 130, 140 has been omitted to illustrate certaininternal structural reinforcements.

As mentioned herein, there may be possible honeycomb applications wherethe top and bottom face sheets 110, 114 comprise different thicknessesand/or materials. For example, the first or top face sheet 110 maycomprise a first thickness and the second or bottom face sheet 114 maycomprise a second thickness wherein the first thickness of the firstface sheet 110 is different than the second thickness of the second facesheet 114. In those cases, there may be structural differences betweenthe two compressed regions depending on the original face sheetthicknesses, the possible addition of doublers (e.g., additional facesheets) to one or the other or both face sheets 110, 114, and whetherthe panel is compressed from the top face sheet 110, the bottom facesheet 114, and/or both. In fact, in certain applications, the doublerscould be tailored in thickness and extent (e.g., a doubler comprising anon-uniform thickness) to meet particular mechanical performancerequirements. The remaining compressed core arrangements discussed inthe present disclosure may comprise such structural differences as well.

As illustrated, the honeycomb panel structure 100 comprises a constantheight (aside from the compressed panel region 102) and the honeycombpanel 100 extends from a first end 104 to a second end 106, the firstcompressed region 102 residing in between the first end and the secondend. Although only one compressed region 102 is illustrated in thisexemplary embodiment of FIG. 3, those of skill in the art will recognizemore than one compressed region may be provided in this honeycomb panel100.

As illustrated in FIG. 3, the compressed core region 102 comprises afully compressed core region. That is, the upper face sheet 110 has beenfully compressed against the core 120 and the bottom face sheet 114. Incertain arrangements and for certain applications and as will bedescribed in greater detail herein, the compressed core region maycomprise a partially compressed core region. That is, in one such apartially compressed core region arrangement, the upper face sheet 110would only be partially compressed against the core 120 and the bottomsurface sheet 114 such that the height of the partially compressedregion would be lower than the un-compressed panel height illustrated inFIG. 3 but yet higher than the compressed core region 102. In certainarrangements and for certain applications and as will be described ingreater detail herein, the compressed core region may comprise alocalized region, such as a localized compressed core region, located onthe panel 100 somewhere between the first and second ends 104, 106.

As can be clearly seen from FIG. 4, the compressed core region 102 ofthe honeycomb panel structure 100 extends along a generally, planarcompressed core region 122 having length L_(CR) 126. This generallyplanar compressed region 122 extends from a bottom portion 132 of afirst ramp or first incline 130 to a bottom portion 142 of a second rampor second incline 140.

The controlled crush or compression of the first region 102 may degradecertain performance characteristics of the core 120 and may therebyresult in a loss of stability in the face sheet 110. To re-establishface sheet stability, the honeycomb panel structure 100 may be providedwith one or more structural reinforcements 145. Specifically, suchstructural reinforcements 145 may comprise one or more weld pins, one ormore a doublers (i.e., one or more additional face sheets), or, in someapplications, perhaps both types of structural reinforcements—i.e., bothpins and doublers.

For example, as also illustrated in FIGS. 3 and 4, various structuralweld pins 150 are provided to support the first ramp 130. Similarly,various structural weld pins 152 are provided to support the secondincline 140. For example, in this illustrated arrangement, six pins areprovided along the first ramp 130 and six pins may also be providedalong the second incline 140.

Aside from providing structural reinforcements along the first andsecond inclines 130, 140 in the form of weld pins, structuralreinforcements may also be provided along the compressed core region102. For example, as illustrated in FIGS. 3 and 4, 16 pins are providedalong the planar compressed core region 122.

As can be seen from FIG. 4, the pins along the first ramp or incline 130extend vertically from the bottom face sheet 114 upwards towards thefirst ramp or incline 130. For example, weld pin 150 a extendsvertically from the bottom face sheet 114 upwards through the core 120towards the inclined top sheet 110. Similarly, the weld pins 152provided along the second incline 140 extend vertically from the bottomface sheet 114 upwards towards the second incline 140.

Aside from providing structural reinforcements along the first andsecond inclines 130, 140 in the form of weld pins 150, structuralreinforcements may also be provided along the compressed core region102. For example, as illustrated in FIGS. 3 and 4, 16 pins are providedalong the planar compressed core region 122. A first type of weld pinmay be used to support the planar compressed core region 122 and asecond, different type of weld pin may be used to support the first andsecond inclines 130, 140, respectively.

Returning to the close up view of compressed panel 100 illustrated inFIG. 4, the compressed region 102 may be provided with weld pins but mayalso be provided with another structural reinforcement by way of adoubler 160 welded along the compressed region. Preferably, the doublercomprises a similar material as the first or top face 110 of thehoneycomb panel 100. In this illustrated arrangement, the doubler 160extends from along the planar compressed region 122 from the bottomportion 132 of the first incline 130 to the bottom portion 142 of thesecond incline 140. In an alternative arrangement, more than one doublermay be provided along the compressed region 102.

Alternatively, again based the design and loading parameters, differentdoubler configurations may also be utilized. As just one example, thedoubler 160 may be provided along the compressed core planar region 122and may extend partially up one or both of the first and second inclines130, 140, respectively. In yet another alternative example, the doubler160 may be provided extending up and over one or both of the inclines.

Additionally, a fastener hole 144 for fastening the honeycomb panel toother structures has been drilled near the middle of the compressedregion 102. This mounting hole may be drilled and may be used to mountan attachment fitting. Although only one fastener hole is illustrated,more than one such hole can be provided.

The location, the orientation, and the number of pins and/or doublersmay vary based on the design load parameters of the honeycomb panelstructure 100 as determined, for example, during component andsubcomponent specification and design. As just one example, in onealternative weld pin configuration, the weld pins 150, 160 may beinstalled perpendicular to the first and second inclines 130, 140,respectively.

For example, FIG. 15 illustrates a perspective view of anotherembodiment of a honeycomb panel structure 500 comprising a compressedcore region 502. In this illustrated embodiment, this compressed coreregion 502 comprises a partially crushed core region. The compressedcore region 502 comprises a core region incline 520 extending from thepartially crushed core region to the top face sheet 512. In addition, aplurality of structural reinforcements 504 are also provided. Suchstructural reinforcements 504 include a plurality of additional facesheets 506, 508, 510 and a plurality of weld pins 532. Specifically, afirst plurality of weld pins are provided to support the first incline520. Similarly, various structural weld pins 532 may be provided tosupport a generally, planar and partially compressed region 530 havinglength designated as L_(PPCR) 526. As can be seen from FIG. 15, certainof these weld pins are oriented so that they extend vertically upwardfrom the bottom face sheet 514 upwards towards the incline 520 (e.g.,weld pin 532 a). In addition, certain of these weld pins are oriented sothat they reside perpendicular to the first incline 520 (e.g., weld pin532 b) and yet other of these weld pins are oriented at different anglesbetween the bottom face sheet 514 and the partially compressed region530 (e.g., weld pin 532 c). As those of skill in the art will recognize,alternative weld pin configurations may also be used.

FIG. 5 illustrates another arrangement of a honeycomb panel structure200 comprising two compressed core regions 202 a, b. The honeycomb panelstructure 200 illustrated in FIG. 5 comprises essentially the samestructure of the honeycomb panel structure illustrated in FIGS. 1 and 2.That is, this honeycomb panel structure 200 comprises a honeycomb core220 assembled between a first or top face sheet 210 and a second orbottom face sheet 214. For ease of illustration, in FIGS. 5 and 6, aportion of the honeycomb core 220 residing between the top face sheetand the bottom sheet 214 along the first and second inclines 230, 240has been omitted to illustrate certain internal structuralreinforcements (i.e., various weld pins).

As illustrated, the honeycomb panel structure 200 comprises a constantheight (aside from the two compressed panel regions 202 a, b) and thehoneycomb panel structure 200 extends from a first end 204 to a secondend 206. The first compressed region 202 a resides near the first end204 and the second compressed region 202 b resides near the second end206. Although the two compressed regions 202 a, b reside near the endsof the honeycomb panel structure 200 is illustrated in this exemplaryembodiment of FIG. 5, those of skill in the art will recognize that yeta third or even a fourth compressed region (similar to the compressedcore region 102 illustrated in FIGS. 3 and 4) may be provided along thishoneycomb panel structure 200 as well.

As illustrated in FIG. 5, the compressed core regions 202 a, b comprisesfully compressed core regions. That is, at both compressed core regions,the top face sheet 210 has been fully compressed against the core 220and the bottom face sheet 214. In certain arrangements and for certainapplications, either or both of the compressed core regions may comprisea partially compressed core region, such as the partially compressedcore region 502 illustrated in FIG. 15.

FIG. 6 illustrates a close up view of the first compressed core region202 a of the honeycomb panel structure 200 illustrated in FIG. 5. Asillustrated in FIGS. 5 and 6, both compressed core regions 202 a, b ofthe honeycomb panel structure 200 extend along a generally, planarcompressed region. For example, the compressed core region 202 a extendsalong a generally, planar compressed core region 222 having lengthL_(CR) 226. This generally planar compressed core region 222 extendshorizontally from the first end 204 of the panel structure 200 to astart 232 of a first ramp or first incline 230. The second compressedcore region 202 b is structured in a similar manner. As illustrated,both the first and the second inclines 230, 240 include generally thesame angle of inclination. However, this does not have to be the caseand may be determined during the specification and design phase of thehoneycomb structure.

The controlled compress or compression of the first compressed coreregion 202 a may damage the core 220 and may thereby result in a loss ofstability in the top face sheet 210. To re-establish and in someinstances increase overall face sheet stability, the honeycomb panelstructure 200 may be provided with one or more structural reinforcements250. Specifically, such structural reinforcements 250 may comprise oneor more weld pins, one or more a doublers (i.e., one or more additionalface sheets), or, in some applications, perhaps both types of structuralreinforcements—both pins and doublers-may be used.

Referring now to the FIGS. 5 and 6, various structural weld pins 255 areprovided to support the first ramp 230. Similarly, various structuralweld pins may be provided to support the second ramp 240. For example,in this illustrated arrangement, six pins are provided along the firstramp 230 and six pins may also be provided along the second ramp 240.

Aside from providing structural support members along the inclines 230,240, structural support members may also be provided along thecompressed core regions 202 a,b. For example, as illustrated in FIGS. 5and 6, eight (8) pins may be provided along the planar compressed coreregion 222. As can be seen from FIGS. 5 and 6, the pins along the firstramp/incline 230 extend vertically from the bottom face sheet 214upwards towards the first incline 230. For example, weld pin 255 aextends vertically from the bottom face sheet 214 upwards through thecore 220 towards the inclined top sheet 210. Similarly, the pinsprovided along the second incline extend vertically from the bottom facesheet 214 upwards towards the second incline 240. The location andnumber of pins may vary based on the loading parameters of the honeycombpanel structure 200 as determined, for example, during component andsubcomponent specification and design. In an alternative weld pinconfiguration, the weld pins may be installed in different orientations,such as perpendicular to the incline.

As noted above, the compressed core panel may be provided with certainstructural reinforcements by way of pins and/or doublers. For example,as can be seen from the close up view of FIG. 6, the compressed region202 a may be provided with weld pins but may also be provided with adoubler 260 along the planar compressed core region 222. One or moredoublers may be provided as well. Preferably, the doubler 260 comprisesa similar material as the top face sheet 210 of the honeycomb panelstructure 200. In this illustrated arrangement, the doubler 260 extendsfrom along the planar compressed region 222 from the first end of thecompressed core region 202 a to a start of the first incline 230. Thesecond compressed core region 202 b of the honeycomb panel structure 200illustrated in FIG. 5 may be similarly structured. Alternatively, and aswill be described and illustrated herein, the second compressed coreregion 202 b of the honeycomb panel may be partially compressed and maybe compressed from one or both honeycomb surfaces.

Alternatively, again based the loading parameters, different doublerconfigurations may also be utilized. As just another example, thedoubler 260 may be provided along the planar compressed core region 222and may extend partially up one or both of the inclines 230, 240. As yetanother alternative, the doubler may be provided that extends up andover one or both of the inclines.

As can be seen more clearly from FIG. 6, a fastener hole 244 forfastening the honeycomb panel to other structures has been drilled nearthe middle of the compressed core region 202 a. This mounting hole maybe drilled and may be used to mount an attachment fitting. Although onlyone fastener hole is illustrated, more than one such hole can beprovided. Again, the second compressed core region 202 b may have asimilar mounting hole configuration.

FIG. 7 illustrates a perspective view of another embodiment of ahoneycomb panel structure 300 comprising a compressed core region 302.The honeycomb panel structure 300 illustrated in FIG. 7 comprisesessentially the same structure as the honeycomb panel structureillustrated in FIGS. 1 and 2. That is, this honeycomb panel structure300 comprises a first or top face sheet 310 and a second or bottom facesheet 314 and a honeycomb core 320 residing between these two sheets.FIG. 8 illustrates an alternative view of the honeycomb panel structure300 with a compressed core illustrated in FIG. 7 wherein the honeycombcore near the incline between the first or top face sheet and the secondor bottom face has been replaced so that the structural reinforcing pins316 a,b,c (FIG. 7) are now no longer visible. For ease of illustration,in FIG. 7, a portion of the honeycomb core 320 residing between the topface sheet incline 315 and the bottom sheet 314 has been omitted to helpillustrate certain internal structural reinforcements (i.e., variouspins 316 a,b,c).

In the illustrated arrangement of FIGS. 7 and 8, the honeycomb panelstructure 300 comprises a completely compressed core region 302. Thatis, the upper face sheet 310 has been fully compressed against the core320 and the bottom face sheet 314 wherein this fully compressed heightis represented by H_(FCC) 328 wherein this height can be compared to theheight of the uncompressed honeycomb panel structure represented byH_(UC) 312. In certain arrangements and for certain honeycomb coreapplications and as will be described in greater detail herein, thecompressed core region in alternative compressed honeycomb arrangementsmay comprise a partially compressed core region wherein the height ofsuch partially compressed core region may comprise any height betweenthe uncompressed core height H_(UC) 312 and the fully compressed heightH_(FCC) 328. Furthermore, although they may not be required in allcompressed honeycomb core applications, this honeycomb panel arrangementis provided with three overlapping doublers 322, 324, 326 near thecompressed portion of the honeycomb panel structure 300.

FIG. 9 illustrates yet another arrangement of a honeycomb panelstructure 330 comprising a compressed core region 332. The honeycombpanel structure 330 illustrated in FIG. 9 comprises essentially the samestructure as the honeycomb panel structure 300 illustrated in FIGS. 7and 8. That is, this honeycomb panel structure 330 comprises a first ortop face sheet 334 and a second or bottom face sheet 336 and a honeycombcore 338 residing between these two sheets.

For ease of illustration, in FIG. 9, a portion of the honeycomb core 320residing between the top face sheet 334 and the bottom face sheet 336along the incline 337 has been omitted to help illustrate certainstructural reinforcements. For example, in this illustrated arrangement,such structural reinforcements comprise internal reinforcements by wayof the various pins 340 a,b,c provided between the incline 337 and thebottom face sheet 336. Additional pins 342 a,b,c may be provided tosupport the planar partially compressed portion of the compressed coreregion 332 and resided between the top face sheet 334 and the bottomface sheet 336. FIG. 10 illustrates an alternative view of the honeycombpanel structure 330 with a compressed core illustrated in FIG. 9 whereinthe honeycomb core near the incline between the first or top face sheetand the second or bottom face has been replaced so that the structuralreinforcing pins are now no longer visible.

In the arrangement illustrated in FIGS. 9 and 10, the honeycomb panelstructure 330 comprises a partially compressed core region 332. Thiscore region is provided with three overlapping doublers 344, 346, 348near the compressed portion of the honeycomb core structure 330. In thispartially compressed core region, the top face sheet 334 has not beenfully compressed against the core 338 and the bottom face sheet 336wherein this partially compressed height is represented by heightH_(PCC) 349 which can be compared to the height of the uncompressed corewhich is represented by H_(UC) 331. As such, the partially compressedcore region may be compressed to a height that is smaller than theuncompressed core height H_(UC) 331 but larger than a fully compressedheight, such as the fully compressed height H_(FCC) 328 of thecompressed core region 302 illustrated in FIGS. 7 and 8.

As noted in the alternative compressed core arrangements illustrated inFIGS. 7-10, complete or partial compression of the core region may takeplace by compressing the top or first face sheet of the honeycomb core.That is, in these arrangements, only the first face sheet may becompressed so as to define an incline while the second face sheet willremain unchanged from its linear state. In alternative compressed corearrangements, compression of the core region may take place on both theupper and the lower face sheets of the honeycomb core. In one suchpreferred arrangement, core compression may take place along the topface sheet as well as the bottom face sheet so as to define a firstincline in the first or top face sheet and a second incline in thesecond or bottom face sheet near the compressed panel region. During ahoneycomb panel compression method, top face and bottom face compressionmay take place simultaneously or serially, that is, one after the other.In addition, such compression may comprise either a complete corecompression (e.g., FIGS. 3-6) or a partial core compression (e.g., FIGS.9-10).

For example, FIG. 11 illustrates a perspective view of anotherembodiment of a honeycomb panel structure 350 comprising a compressedcore region 352. The honeycomb panel structure 350 illustrated in FIG.11 comprises essentially the same structure of the honeycomb panelstructure illustrated in FIGS. 1 and 2. That is, this honeycomb panelstructure 350 comprises a first or top face sheet 360 and a second orbottom face sheet 364 and a honeycomb core 370 residing between thesetwo sheets 360, 364. Honeycomb panel structure 350, as illustrated, hasa similar doubler configuration as the honeycomb panel structure 330illustrated in FIGS. 9 and 10.

For ease of illustration, in FIG. 11, a portion of the honeycomb core370 residing between a first face sheet 360 and a second face sheet andresiding between the first incline 355 and the second incline 369 hasbeen omitted to illustrate certain compressed core structuralreinforcements (i.e., various pins 356 a,b,c,d). FIG. 12 illustrates analternative view of the honeycomb panel structure 350 with a compressedcore illustrated in FIG. 11 wherein the honeycomb core residing betweenthe first incline 355 and the second incline 369 has been removed sothat the structural reinforcing pins 356 a,b,c,d are now no longervisible.

In this arrangement, the honeycomb panel structure 350 comprises acompletely compressed core region 352. Specifically, in thisarrangement, the first or top face sheet 360 is compressed towards thebottom face sheet 364 and the bottom face sheet 364 is compressedtowards the top face sheet 360. As illustrated, the top face sheet 360has been fully compressed against the core 370 and the bottom face sheet364 wherein this fully compressed height is represented by heightH_(FCC) 358 which can be compared to the height of the uncompressed corewhich is represented by H_(UC) 372. In certain arrangements and forcertain applications and as will be described in greater detail herein,the compressed core region in alternative compressed honeycombarrangements may comprise a partially compressed core region wherein theheight of such partially compressed core region may be any heightbetween the uncompressed core height H_(UC) 372 and the fully compressedheight H_(FCC) 358. In this illustrated arrangement, the angle of thefirst incline 355 is generally equivalent to the angle of the secondincline 369. However, in alternative compressed core arrangement,different angle orientations may also be used.

FIG. 13 illustrates yet another arrangement of a honeycomb panelstructure 400 comprising a compressed core region 402. The honeycombpanel structure 400 illustrated in FIG. 13 comprises essentially thesame structure as the honeycomb panel structure 300 illustrated in FIGS.10 and 11. That is, this honeycomb panel structure 400 comprises a firstor top face sheet 404 and a second or bottom face sheet 408 and ahoneycomb core 410 residing between these two sheets. In addition, thehoneycomb panel structure 400, as illustrated, has a similar doublerconfiguration as the honeycomb panel structure 330 illustrated in FIGS.9 and 10.

For ease of illustration, in FIG. 13, a portion of the honeycomb core410 residing between a first incline 414 and a second incline 418 hasbeen omitted to illustrate certain compressed core structuralreinforcements such as incline support pins 420 a, b and compressed coresupport pins 430 a,b,c. FIG. 14 illustrates an alternative view of thehoneycomb panel structure 400 with a compressed core illustrated in FIG.13 wherein the honeycomb core residing between the first face sheetincline 404 and the second or bottom face incline 408 has been replacedso that the structural reinforcing pins 420 and 430 are now no longervisible.

In this arrangement, the honeycomb panel structure 400 comprises apartially compressed core region 402. Specifically, in this arrangement,the first or top face sheet 404 is compressed towards the bottom facesheet 408 and the bottom face sheet 408 is compressed towards the topface sheet 404. As illustrated, the compressed core region 402 comprisesa partially compressed core region. That is, the upper face sheet 404has been partially compressed against the core 410 and the bottom facesheet 408 has also been partially compressed against the core 410. Assuch, the partially compressed height is represented by height H_(PCC)436 which can be compared to the height of the uncompressed core whichis represented by H_(UC) 440. In this illustrated arrangement, the angleof the first incline 414 is generally equivalent to the angle of thesecond incline 418. However, in alternative compressed corearrangements, different angle orientations may also be used.

In this illustrated arrangement, structural reinforcements compriseinternal reinforcements include various pins 420 a,b that are providedbetween the first incline 414 and the second incline 418. Additionalpins 430 a,b,c may be provided to support the planar partiallycompressed portion of the compressed core region 402 and resided betweenthe first face sheet 404 and the bottom face sheet 408.

FIG. 16 illustrates a perspective view of another embodiment of ahoneycomb panel structure 550 with a compressed core region 552. Forexample, FIG. 16 illustrates a first arrangement of a honeycomb panelstructure 550 comprising a compressed core region 552. The honeycombpanel structure 550 illustrated in FIG. 16 comprises essentially thesame structure of the honeycomb panel structure illustrated in FIGS. 1and 2. That is, this honeycomb panel structure 550 comprises a honeycombcore assembled between a first or top face sheet 560 and a second orbottom face sheet 564 and a honeycomb core 568 residing between thesetwo sheets.

Specifically, in this illustrated arrangement, the compressed coreregion of the honeycomb panel structure 550 comprises a localizedcompressed region in the form of a convex shaped compressed region, thatis, a region that curves inwardly. With such a localized convex shapedregion, the honeycomb panel structure 550 need not be compressed near anend of the panel but may be compressed anywhere along a main body of thepanel structure 550, such as at a center of the panel. As describedherein, such a convex shaped compression region may comprise a completecompressed core region or a partially compressed core region.

For example, FIG. 17 illustrates a perspective view of anotherembodiment of a honeycomb panel structure 570 comprising a compressedcore region 572. The honeycomb panel structure 570 illustrated in FIG.17 comprises essentially the same structure as the honeycomb panelstructure illustrated in FIGS. 1 and 2. That is, this honeycomb panelstructure 570 comprises a first or top face sheet 574 and a second orbottom face sheet 576 and a honeycomb core 578 residing between thesetwo sheets. FIG. 18 illustrates an alternative view of the honeycombpanel structure 570 with a compressed core illustrated in FIG. 17wherein the honeycomb core near the compressed core region 572 betweenthe first and second face sheets 574, 576 has been replaced so that thestructural reinforcing pins 579 a, b (FIG. 17) are now no longervisible. For ease of illustration, in FIG. 17, a portion of thehoneycomb core 570 residing between the top face sheet 574 and thebottom sheet 576 near the compressed core region 572 has been omitted tohelp illustrate certain internal structural reinforcements (i.e.,various pins 579 a, b).

In the illustrated arrangement of FIGS. 17 and 18, the honeycomb panel570 comprises a completely compressed core region 572. That is, the topface sheet 574 has been fully compressed against the core 578 and thebottom face sheet 576 is previously described herein. As discussedherein, the compressed core region 572 may further include structuralreinforcements by way of one or more doublers 562 a,b,c.

FIG. 19 illustrates a perspective view of another embodiment of ahoneycomb panel structure 580 comprising a compressed core region 588.The honeycomb panel 580 illustrated in FIG. 19 comprises essentially thesame structure as the honeycomb panel structure illustrated in FIGS. 1and 2. That is, this honeycomb panel structure 580 comprises a first ortop face sheet 582 and a second or bottom face sheet 586 and a honeycombcore 584 residing between these two sheets. FIG. 20 illustrates analternative view of the honeycomb panel structure 580 with a compressedcore illustrated in FIG. 19 wherein the honeycomb core 584 near thecompressed core region 588 between the first and second face sheets 582,586 has been replaced so that the structural reinforcing pins 579 a, b(FIG. 19) are now no longer visible. For ease of illustration, in FIG.19, a portion of the honeycomb core 584 residing between the top facesheet 582 and the bottom face sheet 586 near the compressed core region584 has been omitted to help illustrate certain internal structuralreinforcements (i.e., various pins 590 a,b,c,d).

In the illustrated arrangement of FIGS. 19 and 20, the honeycomb panelstructure 580 comprises a partially compressed core region 588. That is,the upper face sheet 582 has only been partially compressed against thecore 584 and the bottom face sheet 586 is previously described herein.

FIG. 21 is an illustration of a flow diagram of an embodiment of amethod 600 of the disclosure for making one of the embodiments of thecompressed honeycomb core as disclosed herein using a honeycomb panelstructure, such as the honeycomb panel structures illustrated herein.The method 600 comprises step 602 of defining certain general designcriteria for the compressed honeycomb panel structure. As just oneexample, such design criteria might relate to the type of face sheetsused by the honeycomb panel or relate to the thickness of the facesheets so these sheets are designed to handle the tensile, compressive,and shear stresses caused by the anticipated design load. In addition,the honeycomb core should be strong enough to withstand any shearstresses caused by the design loads. Moreover, in certain applications,the metallic bond or weld between the face sheets and the honeycomb corealong with the structural reinforcements (as discussed in detail above)are designed to possess enough strength to carry shear stress into thecore.

Additional general design criteria from step 602 could also related tothe anticipated loading conditions of the honeycomb panel structure,including uniform distributed loads, end loading, point loading andpossibly impact loads. Other design criteria could also include thehoneycomb panel type (e.g., cantilever, simply supported), physical andspace constraints including weight limit, thickness limit, deflectionlimit, and perhaps safety factors.

The method 600 also includes the step 608 of selecting a honeycomb panelstructure. Such honeycomb panel structure may have a generally planarconfiguration or alternatively may have a different shape. Such ahoneycomb panel structure may utilize a first face sheet and a secondface sheet having similar or perhaps dissimilar material and/ormechanical properties. The method 600 also comprises the step ofselecting a tooling arrangement at step 606 and also comprises the step604 of selecting whether a certain type of structural reinforcements,such as doublers, are needed. If at step 604 the method determines thatdoublers are needed, then at step 608, these selected doublers arelocated in the selected tooling.

Once the doublers (if required) and the honeycomb material has beenplaced into the tooling at steps 608 and 612, the method 600 thenperforms a controlled compress of the honeycomb structure at steps 610and 614 so as to achieve a desired compressed core shape having adesired compression depth as discussed in detail herein. As mentionedabove, this controlled compress may take place along one or moreselected portions or regions of the honeycomb panel. (i.e., an endregion or a localized region). Moreover, this compression may take theform of a partial compression or a complete compression. Then, at step616, the doublers are positioned on the compressed core for joiningthese two components, such as by welding.

Compression at steps 610 and 614 may take the form of either a hot orcold compression with tooling. The specific material used in thehoneycomb core and the face sheets will tend to dictate if forming isaccomplished in the “cold” or “hot condition. As those of ordinary skillin the art recognize, some materials are “cold” formable and others arenot. Methods of hot forming include hot presses other methods of formingin a controlled thermal environment. In the cold condition, there aretwo die faces that have the desired final shape of the part.

For example, FIG. 22 illustrates on cold forming arrangement 700 thatmay be used for compressing a honeycomb panel structure and/or doubler.In this arrangement, the forming arrangement comprises a first or upperdie portion 702 and a second or lower die portion 704. Initially, thedie portions 702, 704 are separated, and the honeycomb panel structureis placed into the first and second dies. These dies are then are forcedtogether so as to form a compressed core 720, as illustrated in FIG. 23.As illustrated in FIG. 23, the first and second dies of FIG. 21compressing a honeycomb core so as to define a compressed core portion714. As illustrated, this compressed core portion comprises a partiallycompressed core portion 714 with a first incline 708 as discussedherein. Alternatively, the method may comprise the step of partiallyforming and then stress relieving the part prior to further formingsteps.

Alternatively, if a hot condition is used to form the compressed core,the die surfaces are heated as well as the part itself. The hot diesurfaces are then forced together to the extent desired. This may beaccomplished using a heated press or inflating bladders that use gaspressure to translate one or both die surfaces. As just one example,such tooling may comprise essentially a press structure having two diefaces wherein these die faces come together under load so as to compressthe honeycomb core.

Moreover, and as noted above, in one arrangement, the core may becompressed only from the top of the honeycomb core or only from thebottom of the core. Alternatively, the core may be simultaneouslycompressed from both the top and bottom directions.

Returning to the method 600 illustrated in FIG. 21, after the honeycombpanel structure is compressed, the method further comprises step 620where it is determined if structural re-enforcements by way of pins areto be provided to the compressed honeycomb panel. If structuralenforcements by way of pins are required, at step 622 it is determinedat step 622 where these pins are to be located are to be provided alongthe panel, and how many of the enforcements are to be used.

For example, in the situation where the compressed core requires weldpins, at step 622, a number of weld pin holes are drilled in the desiredhoneycomb panel area. This desired area could be the compressed region,the non-compressed region, or both types of regions of the honeycombpanel. At step 626, the pins are then inserted into the first facesheet, through the compressed core, and the second face sheet. At step630, the method 300 also includes the step of welding the pin or pins tothe second face sheet. Then, at step 634, the method includes the stepof cutting the pin above the first or top face sheet. Thereafter, atstep 638, the pin is welded to the first or top face sheet. The step ofinserting and welding the pins in place may be repeated at step 650.

Once the desired structural reinforcements have been fabricated andwelded onto the structure, the method 600 may further includes the stepof determining whether the general design criteria determined requires amounting hole. If one or more mounting holes are required, the hole isdrilled. Thereafter, the honeycomb panel is assembled by either beingmounted to an external structure or provided with an attachment fittingfor structural mounting.

The embodiments of the disclosed compressed sandwich structures with theintentionally compressed honeycomb core and embodiments of the methodfor making the same have numerous advantages. For example, the compositesandwich structure as disclosed herein reduces the overall weight of astructure by avoiding the use of heavier materials to facilitatestrength to bear concentrated loads. The metallic sandwich structurealso further reduces weight of a structure by eliminating the need forcostly machined attachment fittings. Moreover, the compressed honeycombcore also reduces costs by way of a reduced “buy to fly” ratio ofmaterial purchased to machine attachment fittings. That is, thecompressed honeycomb core does not require an undesirable amount laboror machining in order to prepare the panel for final installation intothe components and subassemblies, such as in airplane components andsubassemblies.

Furthermore, the compressed honeycomb core will reduce costs byeliminating the labor costs and machining time of fabricating attachmentfittings typically associated with conventional honeycomb panelstructures. As such, the compressed honeycomb core will also furtherreduce costs by eliminating the cost of additional cutting tools andrelated maintenance expenses.

Furthermore, the compressed honeycomb core will reduce the total cycletime of component and subassembly structures by eliminating thefabrication time necessary to manually cut out honeycomb panels sectionsfor the attachment fittings. As such, the presently disclosed honeycombpanels and methods will also reduce the amount of time and expense forwelding these attachment fittings to the cut out honeycomb core.

The description of the different advantageous embodiments has beenpresented for purposes of illustration and description, and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different advantageousembodiments may provide different advantages as compared to otheradvantageous embodiments. The embodiment or embodiments selected arechosen and described in order to best explain the principles of theembodiments, the practical application, and to enable others of ordinaryskill in the art to understand the disclosure for various embodimentswith various modifications as are suited to the particular usecontemplated.

We claim:
 1. A method of forming a honeycomb panel structure comprisingthe steps of: compressing the honeycomb panel structure in a first panelregion, wherein the first panel region comprises an incline face sheetand a bottom face sheet, and wherein the incline face sheet is at anacute angle to the bottom face sheet; reinforcing at least a portion ofthe first panel region; drilling a plurality of holes in the first panelregion; and inserting a plurality of pins into the first panel region,wherein a first pin of the plurality of pins is perpendicular to theincline face sheet, and wherein a second pin of the plurality of pins isperpendicular to the bottom face sheet.
 2. The method of claim 1,further comprising: drilling a plurality of holes in an uncompressedpanel region adjacent to the first panel region; inserting a secondplurality of pins into the uncompressed panel region; and welding thesecond plurality of pins into a face sheet of said honeycomb panelstructure.
 3. The method of claim 1 wherein the step of reinforcing atleast a portion of the first panel region comprises the steps of:utilizing at least one welded pin to add at least one additional facesheet to the honeycomb panel structure.
 4. The method of claim 1 whereinthe honeycomb panel comprises a metallic honeycomb panel.
 5. The methodof claim 1 further comprising the step of welding the plurality of pinsinto a face sheet of the honeycomb panel structure.
 6. The method ofclaim 1, further comprises the step of: compressing the honeycomb panelstructure in a second region that is distinct from the first region. 7.The method of claim 1 wherein the honeycomb panel structure has anun-compressed panel height in the uncompressed panel region, wherein thestep of compressing the honeycomb panel structure in the first regioncomprises compressing the honeycomb panel structure so that the heightof the compressed honeycomb panel structure is a fully-compressed heightthat is lower than the un-compressed panel height and lower than apartially-compressed height.
 8. The method of claim 1 wherein thehoneycomb panel structure has an un-compressed panel height in theuncompressed panel region, wherein the step of compressing the honeycombpanel structure in the first region comprises the step of partiallycompressing the honeycomb panel structure in the first region to form apartially compressed region with a height in the partially compressedregion is lower than the un-compressed panel height and is higher than afully-compressed height.
 9. The method of claim 1 wherein the honeycombpanel structure comprises at least one substantially planar shape. 10.The method of claim 1 wherein the first panel region comprises an endregion of the honeycomb panel structure.
 11. The method of claim 1wherein the first panel region comprises a localized region of thehoneycomb panel structure.
 12. The method of claim 1 wherein the inclineface sheet has a first thickness, wherein the bottom face sheet has asecond thickness that is different that the second thickness.
 13. Themethod of claim 1 further comprising the step of attaching at least oneadditional face sheet to at least a portion of the compressed coreregion.
 14. The method of claim 13 wherein the at least one additionalface sheet comprises a first metal and honeycomb panel structurecomprises a second metal, the second metal different than the firstmetal.